Multiple Antennas

Future generations of cellular communications requires higher data rates and a more reliable
transmission link with the growth of multimedia services, while keeping satisfactory quality of service, .
MIMO antenna systems have been considered as an efficient approach to address these demands by
offering significant multiplexing and diversity gains over single antenna systems without increasing
bandwidth and power. Although MIMO systems can unfold their huge benefit in cellular base stations,
but they may face limitations when it comes to their deployment in mobile handsets.
To overcome this drawback, relays (fixed or mobile terminals) can cooperate to improve the overall
system performance in cellular networks. Cooperative communications can efficiently combat the severity
of fading and shadowing through the assistance of relays. It has been found that using relays the capacity
and coverage of cellular networks can be extended without increasing mobile transmit power or
demanding extra bandwidth.

Using an isomorphism between the mul- tiuser detection problem and transmission of informa- tion over MIMO channels coupled to recent results on optimal signature waveform construction, we provide a new approach to information transfer in multiple antenna systems. The approach is based on a multi- carrier modulation scheme at each transmit antenna with sinusoids as carriers, which leads to a

Abstract—The maximum traffic arrival rate at the network for a given delay guarantee (delay constrained throughput) has been well studied for wired channels. However, few results are available for wireless channels, especially when multiple antennas are employed at the transmitter ...

The role of the Advanced Air Transportation Technologies program undertaken at the NASA Glenn Research Centers has been focused mainly on the improvement of air transportation safety, with particular emphasis on air transportation communication systems in on-board aircraft. The conventional solutions for digital optical communications systems specifically designed for local/metro area networks are, unfortunately, not capable of transporting the microwave and millimeter RF signals used in avionics systems. Optical ...

We address the problem of space-time codebook design for non-coherent communications in multiple-antenna wireless systems. In contrast with other approaches, the channel matrix is modeled as an unknown deterministic parameter at both the receiver and the transmitter, and the Gaussian observation noise is allowed to have an arbitrary correlation structure, known by the transmitter and the receiver. In order to handle the unknown deterministic space-time channel, a generalized likelihood ratio test (GLRT) receiver is considered. A new methodology for space-time codebook design under this non-coherent setup is proposed. It optimizes the probability of error of the GLRT receiver’s detector in the high signal-to-noise ratio (SNR) regime by solving a high-dimensional nonlinear non-smooth optimization problem in a two-step approach. (i) Firstly, a convex semidefinite programming (SDP) relaxation of the codebook design problem yields a rough estimate of the optimal codebook. (ii) This is th...

Abstract. A High Data Rate (HDR) system has been proposed for providing downlink wireless packet service by using a channel-aware scheduling algorithm to transmit to users in a time-division multiplexed manner. In this paper, we propose using multiple antennas at the transmitter ...

Abstract: Traditional approaches in the analysis of downlink systems decouple the precoding and channel estimation problems. However, in cellular systems with mobile users, these two problems are in fact tightly coupled. In this paper, this coupling is ...

In this paper, performance of providing WiMAX from high altitude platforms (HAPs) with multiple antenna payload will be investigated as well as considering the coexistence capability with multiple-operator terrestrial deployments. A scenario of a HAP and terrestrial WiMAX base stations deployed inside a HAP coverage area with a radius at 30 km will be proposed. HAP cellular formation with different

Capacity in wireless channels has become the prime aspect in mobile communications. Significant improvements are possible with MIMO channels -the use of multiple antennas at both the transmitter and receiver-. Reception in this type of channels is achieved with space-time coding by jointly designing channel coding, modulation and equalization, allowing an important increase in the throughput of band-limited wireless channels.

In this paper we analyze the performance of multiple relay channels when multiple antennas are deployed only at relays. We apply two antenna diversity techniques at relays, namely maximum ratio combining (MRC) on receive and transmit beamforming (TB). We show that with K relays the network can be decomposed into K diversity channels each with a different channel gain, and that the signals can be effectively combined at the destination. We assume that the total number of antennas at all relays is fixed at N. If the total transmit power for all relays are the same as for the source and equally distributed among all the relays, the network capacity will be lower bounded by that of N relay channels each with single antenna, and upper bounded by that of single relay channels with N antennas.

A general statistical model for correlated MIMO chan-nels is described. It will be valid for all kinds of algorithms using multiple antennas. The channel correlations are de-rived for the case of a flat fading environment. It is shown, that these correlations can be created in a statistical model by simply multiplying spatially uncorrelated channel matri-ces with the square roots of two covariance matrices. The result is generalized to the frequency selective case. In the following this model is used in Monte-Carlo simulations to compute MIMO capacities depending on the angular spread and the element spacing at the receive and transmit antenna array.

Interference between nodes is a critical impairment in mobile ad hoc networks. This paper studies the role of multiple antennas in mitigating such interference. Specifically, a network is studied in which receivers apply zero-forcing beamforming to cancel the strongest interferers. Assuming a network with Poisson-distributed transmitters and independent Rayleigh fading channels, the transmission capacity is derived, which gives the maximum

... I. Fatani, F.-X. Coudoux, P. Corlay IEMN (UMR 8520), Department OAE, UVHC VALENCIENNES CEDEX (FRANCE) imade-fahd-eddi.fata@univ ... can verify the well-known “cliff effect” in the case of single description coding: decoded video quality becomes very bad when error ...

The ever increase in demand for bandwidth and services related to high performance broadband wireless communications has opened the doors for use of multiple antennas both at the transmitter and the receiver. The wireless channel properties are dynamic by nature as it is frequency selective as well as time dependent. MIMO channel estimation technique has been one among the prime focus areas among the researchers in past two decades, which has emerged as one among the novel techniques to support the ever increase in demand for bandwidth as well as high data rate to support upcoming telecom and multimedia services. Combination of MIMO with OFDM as well as UWB techniques has shown improved performance in providing high data rate with low complex receiver properties and channel capacity. Recently researchers have shown interest in applying MIMO-OFDM in estimating channel parameters of underwater acoustic channels. The objective of the present paper is to present the developments made by...

Multiple-input-multiple-output (MIMO) technology will be used by fourth generation mobile networks (also called Long Term Evolution — LTE) to achieve very high data rates in both the uplink and downlink channels. MIMO is based on the use of multiple antenna systems within the mobile terminal as well as the base station. Such antenna systems are required to fit within the hand-held (mobile) terminal which occupies a small size (typically not more than 60 × 100 mm2). Antenna integration and miniaturization are two major challenges. We propose an electrically small antenna (ESA) that is based on the meander antenna structure that operates in the 800 MHz band of LTE and 3G cellular standards. The antenna has a measured center frequency of 897 MHz, bandwidth of 185 MHz and total size of 23.5 × 43 mm2. In addition, we present the design of a dual element MIMO antenna system based on the ESA antenna designed. The dual element MIMO antenna system covers the bands from 760–886 MHz and occupi...